Dental casting machine



y 7, 1935. c. s. M HORN 2,000,801

DENTAL CASTING MACHINE Filed Dec. 15, 1932 3 Sheets-Sheet 1 N F K b 31} r 1 m o 0* t W T( H 1' @96 9 v *1 L EL E H W Q N o I I\- 1 EL I I a a ,5. IL Zhwentor attorneys May 7, 1935. c. s. VAN HORN .7 2,000,801

DENTAL CASTING MACHINE Filed Dec. 15, 1952 3 Sheets-Sheet 2 ulllu ill.

5:? V 3nventor 1 7 attorneys May 7, 1935.

C. S. VAN HORN DENTAL GAS/TING MACHINE Filed vac. 15, 1932 5 Sheets-Sheet 3 a: S Zmventor Gttomegs Patented 'May 7, 1935,

UNITED STATES PATENT OFFICE 2,000,801 DENTAL CASTING MACHINE Chris S. Van Horn, Bloomsburg, Pa. Application December 15, 1932, Serial No. 647,449

6 claims. (c1. 22-051) 7 This invention relates to centrifugal machines such as used in making dental castings and the like to definite dimensions, its object being to provide a casting machine in which the mold is .5 rotated in a vertical plane but is so supported and 5 a predetermined angle and rotating the same in a vertical plane the gold will bev directed by centrifugal force into the mold without undesirable agitation, the angle of the ingate and mold relative to the path of movement being such as to insure proper direction of the full compression force incident to the circular motion and the resultant tangential influence.

A further object is to provide a motor for operating the arm assembly, means being employed whereby when the motor is to be started the application of heat to the flask will be stopped automatically and the flask shifted to pouring position.

A further object is to control the forces to which the molten metal is subjected, at all times during the casting operation so as to avoid any abrupt or jerking action which might tend. to agitate the liquid gold to an undesirable extent, and to maintain the gold under a constant uniform pressure during its change of state to insure a sharply defined casting. L

A still further object is to maintain the flask, ingate and mold at such an angle during the; rotation thereof that the liquefied gold will be subjected to compressive force exerted along the same path which the gold would be thrown naturally by centrifugal force should it be unrestrained.

With the foregoing and other objects in view 0 which will appear as the description proceeds, the

invention consists of certain novel details of construction and combinations of parts and'certain steps of the method hereinafter more fully described and' pointed out in the claims,it being understood that changes may be made in the construction and arrangement of the parts without departing from the spirit of the invention as claimed.

In the accompanying drawings the preferred form of the invention has been shown.-

tor merely opens the valve III by means of han- In said drawings: Figure 1 is a front elevation of the machine,

the flask being shown in its normal position over a heater in the form of a Bunsen burner.

Figure 2 is a side elevation. Figure 3 is a view similar to Figure ,1 showing the relative position of the parts immedi-- ately following the movement of the starting switch. 4

Figure 4 is a side elevation illustrating the parts in the positions shown in Figure 3.

Figure 5 is a rear elevation.

Figure 6 is a section through the inverted flask with the crucible-ingate former in position therein and supporting a sprue-wire on which a pattern is mounted.

Figure '7 is a plan view of the structure shown in Figure 6.

Figure 8 is a section showing the crucible,

ingate and mold produced by the useof the as-' sembly shown in Figures 6 and 7.

Figure 9 is a plan view of the structure shown in Figure-8.

mally to cut out the motor." The switch is held 3 in this normal or cut out position by a spring 5 mounted on and secured to the shaft 4 and.

a supporting arm 6 is carried by the shaft and is normally held in an upwardly inclined position as shown in Figures 1 and 2. This arm has an angular terminal portion! constituting a flask bucket support and stop as hereinafter explained.

A heating device, which can be a Bunsen bumer, 8, is fixedly supported where it will heat the flask and investment while supported, by arm 6 and a gas pipe 9 leading to this burner has a valve lllthe stem ll of which hasa handle I? whereby the valve can be opened at will. A chain or other suitable flexible connection I3 is attached to the stem and to the shaft'l. This connection serves to ;rotate stem II and its valve when the shaft 4 is rotated ,to close the motor circuit, such action resulting in shutting off the gas to the burner. When the motor is not operating and the burner is shut off the connection I3 is slack. Should itbe desired to light the gas at the burnerthe operadle' l2. This pulls the connection l3 taut and supplies gas to the burner where it can be ignited.

The shaft ll of the motor I is secured to the intermediate portion of an arm l5. One end of this arm is provided with a fork l6 while the other end can be weighted, as at "5, so as to practically counter-balance the fork and the parts carried thereby.

Tiltably mounted in the fork I6 is a flask bucket I! having one end and a portion of its top open or, cut away as indicated at l8 while its bottom preferably is formed with large openings l8 through which heat can pass directly to the contents of the bucket. The closed end of the bucket overbalances the open end, thereby insuring prompt tilting of the bucket from the position shown in Figure 1 to the position shown in Figure 3 when said bucket is relieved of its supporting arm 6.

.To produce the crucible, ingate and mold it is preferred to use a flask l9 open at the bottom and provided with a circular opening 20 in its top; the two ends, the .sides and that portion of the top back of the circular opening being, as in the construction shown, free to move outwardly under the pressure executed by the contained investment when expanding during its setting period and the subsequentthermal expansion when heated, thus assuring predee termined accuracy in the required voluminal dimensions of the mold by admitting unrestrained expansion of the investment; it being noted that in rigid flasks, the investment expansion is restrained and the mold subject to warpage and indefinite voluminal dimensions. A hollow substantially spherical crucible former 2| is adapted to be inserted into the opening and is provided with an annular flange 22 which will rest on the flask. A spring clip 23 can be attached to the flange for engaging in a notch 24 so as to hold the former against displacement.

The former has a projection 25 extending therefrom and constituting the ingate former. An opening 26 is extended through this projection and is adapted to receive a sprue-wire 21 with a reduced end 28 on which the pattern 29 is supported. A set screw 30 is carried by the former for binding upon the sprue-wire to hold it against movement relative to the former.

In practice the pattern is first produced of wax or other suitable material and applied to the end of the sprue-wire. Said wire is then inserted into the projection or ingate former 25 and fastened by means of the set screw 30. Thereafter the former 2 i-25 is tilted so that the pattern and the ingate former can first be inserted through opening 20 into flask I 9. The flange 22 of the former is thereafter. brought to position against the flask where it is held by the clip 23...

With the parts assembled as described the flask is inverted to the position shown in Figure 6. It.

is to be understood that the pattern can be coated in any manner desired or required before it is inserted into the flask.

Following the foregoing operation the mixed investment is poured into the flask around the former 2l--25 and the coated pattern 29 so as to completely fill the flask, it being understood that the mixed investment can be-easily worked into place to prevent the formation of undesirable cavities or crevices.

After the investment has hardened the set screw ii is rotated to free the sprue-wire 21 and said wire is then drawn back .into the former 2|, thereby withdrawing from the pattern until the projecting end of the sprue-wire has been retracted into the former :5. The entire ror'mercan then be tilted out of the cavity in the investment through opening 20 thereby-leaving in said investment a crucible 3|, and ingate 32.

The flask is now placed, preferably, in an oven and by degrees dried, the wax burned out and 5 mold temperature raisedv'to the desired temperature to realize the thermal expansion of the investment. The flask is subsequently placed in the flask bucket I1, and the heat from the Bunsen burner underneath and the blow-pipe flame used 10 to fuse the gold in the crucible, maintains the mold temperature, since if there is a drop in mold temperature before casting there will be a corresponding shrinkage in the mold, hence a casting which is too small. The supply of gas to the 5 burner is turned on by pulling downwardly on handle l2. As before explained this action also pulls taut the connection l3. The parts are now in the positions shown in Figures 1 and 2 and there remain until the gold has been liquefied in 20 the crucible by the blow-pipe flame.

The operator next shifts the switch 3 from its normal position. This rotates shaft 4 and simultaneously moves the arm 6 downwardly and pulls through connection l3 upon the valve stem II to 25 shut off the flame at the burner. Thus the bucket and the flask therein will be tilted downwardly relative to the fork l6 and arm l5. It has been found in practice that the most efficient angle of the flask when tilted is approximately 30 twelve degrees relative to the longitudinal axis of the arm l5. This initial tilted position has been illustrated in Figures 3 and 4. By tilting the flask initially to this angle the liquefied gold in the crucible will be caused to fiow by gravity 35 into the ingate and mold and the gold will be placed in the most favorable position toreceive the full force incident .to circular motion and tangential influence properly directed.

The time interval between the horizontal and 40 tilted positions of the flask may be varied to meet conditions. Thestarting motion should be rather deliberate because any sudden or jerking motion would tend to spill-the liquefied gold from the crucible and also cause unnecessary agitation of 45- the gold and interfere with its smooth and rapid flow into the mold.

As the mold is first filled by gravity, there is produced a poured casting but without sufiicient pressure to effect sharp definition in the resultant 50 casting. Thus it is essential, in order to complete the casting operation, to subject the contents of the ingate and the mold to the action of centrifugal force. 4

If, while a wheel is revolving uniformly, a 55' 'Wheg, the flask is thus inclined the liquefied gold in 'the ingate and mold is directly in the lines 65 of force, defined by the path along which areleased particle would fly when subjected to centrifugal action and as the ingate'and mold offer no restraint to such movement the gold will be uniformly forced into the mold and con ipressed against the walls thereof, the pressure being uniformly maintained" throughout the entire change of state of the gold from a liquid to its solid state.

As the gold is compressed in the mold along the natural path determined by the forces set up through the rotation of the mold there will be no undesirable interference and resultant agitation. On the contrary the gold will be maintained under a constant even pressure, insuring sharp definition of the casting.

It is to be understood that the rotation of the flask, ingate and mold follows immediately after the tilting thereof and can continue for as long a period as desired after which the flask can be brought to a stand, removed from the bucket, and the investment broken out to release the 1 cas ing. The parts are reset by placing the buc et on the stop am where it is ready to receive another flask with the formed mold therein.

What is claimed is: V

l. The method of obtaining a sharply defined casting of uniform texture and definite dimensions which includes the step of supporting a flask and contained investment in a substantially horizontal position, heating the flask and investment, while in such position, to fuse and liquify the metal in the crucible therein, thereafter gradually tilting the flask manually to cause the molten metal to flow smoothly but en masse from the crucible through an ingate to the mold, and

subsequently rotating the flask to create centrifugal force, the flask, when tilted, being at such an angle as to maintain the ingate and mold along lines substantially parallel with the lines of force incident to the rotary motion.

2. The method of obtaining a sharply deflned casting of uniform texture and definite relative dimensions which includes the step of heating a stationary supported flask and contents, to fuse and liquify the metal in the crucible therein, thereafter gradually tilting the flask manually to cause the molten metal to flow smoothly but en masse from the crucible through an ingate'to the mold, and subsequently rotating the flask and contents with an initial gentle impulse and at a gradually increasing speed to subject the liquid metal to the action of centrifugal force without agitation, the flask, when tilted, being at such an angle as to maintain the ingate and mold along lines substantially parallel with the lines of force incident to rotary motion, thereby to maintain the metal under uniform compression without agitation during the change ofstate of the cooling metal.

3. ll centrifugal casting machine including .a support mounted for rotation,-a heating element, holding means carried by the support, a flask and contents supported thereby above the heating element and manually tiltable relative to said support, and means under the control of an operator for successively relieving the flask and contents from the action of the heating element, re-' leasing the flask, crucible, ingate and mold for tilting to a predetermined angle relative to the support, thereby to deliver the fused contents en masse from the crucible to the ingate and mold, and rotating the support and flask.

4. In a centrifugal casting machine the combination with amotor, a rotatable support carried thereby and a bucket tiltably connected to the support, of a flask removably mounted in the bucket and provided with a crucible,-an ingate and a mold, means for holding the bucket and flask normally in substantially horizontal positions, an element for heating the flask while in normal position thereby to maintain mold temperature and to melt the contents of the crucible, and separate means under the control of an operator for successively relieving the flask from the action of the heating element, releasing the flask for tilting thereby to pour the liquid contents of the crucible en masse through the ingate into the mold, and thereafter to start the motor to rotate the support and flask thereby to automatically move the flask to such position relative to the support as to place the liquid under pressure along lines substantially parallel with the lines 'of force incident to the rapid rotation of the support.

5. A centrifugal casting machine including a support, a member carried by the support for holding a flask, crucible, ingate and mold, said member, when stationary, being in substantially horizontal position, and means for rotating said support-to tilt said member automatically into position to maintain the liquid metal under pressure in the ingate and mold along lines substantially parallel with the lines of force incident to the rapid rotation of the support.

6. A centrifugal casting machine including a support, a member carried by the support for holding a flask, crucible, ingate and mold, said member, when stationary, being in substantially horizontal position, means for heating the flask while held stationary, thereby to fuse and liquefy the metal contents of the flask, and means for rotating said support to tilt said member automatically into position to maintain the liquid metal under pressure in the ingate and mold 

